qcc is not a compiler. It's just a QNX front end tool for calling a compiler (in your case gcc) and libraries (Dinkum in your case).

-lang-c++ is indeed an option to qcc ('use qcc' to see all options).

There is nothing special when changing to Dinkum other than specifying the option to qcc to use Dinkum. I would imagine the '.h' you are having trouble with would be the same for any compiler since they are standard files...